Fig. 1. Effect of microinjection of l-glutamate sodium into the hypothalamic paraventricular nucleus (PVH) (A) or into the region nearby the PVH (B) on acupuncture analgesia in the rat. Acupuncture means the animals which “Zusanli” points (St. 36) were given electrical acupuncture (dense-disperse wave, f₁ = 10 Hz, f₂ = 20 Hz, 2–3 V) for 30 min. The change of pain threshold (%) indicates: [(the present pain threshold − the pain threshold before electrical acupuncture)/the pain threshold before electrical acupuncture] × 100. Control group, microinjection of 1 μl artificial cerebra spinal fluid into the PVH (×, n = 9); first experimental group, microinjection of 50 μg l-glutamate sodium/1 μl artificial cerebra spinal fluid into the PVH (, n = 9); second experimental group, microinjection of 100 μg l-glutamate sodium/1 μl artificial cerebra spinal fluid into the PVH (A) or the region nearby the PVH (B) [○, n = 9 (A) or 10 (B)]; third experimental group: microinjection of 150 μg l-glutamate sodium/1 μl artificial cerebra spinal fluid into the PVH (■, n = 9); and fourth experimental group, microinjection of 200 μg l-glutamate sodium/1 μl artificial cerebra spinal fluid into the PVH (, n = 9). n indicates the animal number in each group. The results are showed as mean ± S.E.M. ^*P < 0.05, ^**P < 0.01 and ^***P < 0.001 are for the comparison of change of pain threshold (%) from the experimental group and the control group.

Fig. 2. Effect of microinjection of l-glutamate sodium into the hypothalamic paraventricular nucleus (PVH) on acupuncture analgesia in the de-pituitary rat. Acupuncture means the animals which “Zusanli” points (St. 36) were given electrical acupuncture (dense-disperse wave, f₁ = 10 Hz, f₂ = 20 Hz, 2–3 V) for 30 min. The change of pain threshold (%) indicates: [(the present pain threshold − the pain threshold before electrical acupuncture)/the pain threshold before electrical acupuncture] × 100. Control group, microinjection of 1 μl artificial cerebra spinal fluid into the PVH (×, n = 9); experimental group, microinjection of 100 μg l-glutamate sodium/1 μl artificial cerebra spinal fluid into the PVH (○, n = 9). n indicates the animal number in each group. The results are showed as mean ± S.E.M. ^*P < 0.05, ^**P < 0.01 and ^***P < 0.001 are for the comparison of change of pain threshold (%) from the experimental group and the control group.

Fig. 3. Effect of microinjection of l-glutamate sodium into the hypothalamic paraventricular nucleus (PVH) on (A) arginine vasopressin (AVP), (B) oxytocin (OXT), (C) leucine enkephaline (L-Ek), (D) β-endorphin (β-Ep) and (E) dynorphinA_1–13 (DynA_1–13) concentrations in the PVH perfuse liquid using radioimmunoassay. Glutamate means the artificial cerebra spinal fluid containing 100 μg l-glutamate sodium was perfusing into the PVH in 20 min using push–pull perfusion. The change of peptide (AVP, OXT, L-Ek, β-Ep or DynA_1–13) concentration (%) indicates: [(the present peptide concentration − the peptide concentration before the artificial cerebra spinal fluid containing 100 μg l-glutamate sodium was perfuse)/the peptide concentration before the artificial cerebra spinal fluid containing 100 μg l-glutamate sodium was perfuse] × 100. Control group, only artificial cerebra spinal fluid, no l-glutamate sodium was perfuse (×, n = 8); experimental group, the artificial cerebra spinal fluid containing 100 μg l-glutamate sodium was perfuse in 20 min (○, n = 8). n indicates the animal number in each group. The results are shown as mean ± S.E.M. ^*P < 0.05, ^***P < 0.001 are for the comparison of the change of the peptide concentration (%) from experimental group and the control group.

Fig. 4. Effect of intraventricular injection of (A) anti-arginine vasopressin serum (AAVPS), (B) anti-oxytocin serum (AOXTS) or (C) naloxone on the microinjection of l-glutamate sodium into the hypothalamic paraventricular nucleus (PVH) enhancing acupuncture analgesia. Acupuncture means the animals which “Zusanli” points (St. 36) were given electrical acupuncture (dense-disperse wave, f₁ = 10 Hz, f₂ = 20 Hz, 2–3 V) for 30 min. The change of pain threshold (%) indicates: [(the present pain threshold − the pain threshold before electrical acupuncture)/the pain threshold before electrical acupuncture] × 100. First group, intraventricular injection of 10 μl normal rabbit serum (NRS) [(A) and (B)] or 10 μl artificial cerebra spinal fluid (ACSF) (C) + microinjection of 1 μl ACSF into the PVH (×, n = 8); second group, intraventricular injection of 10 μl NRS [(A) and (B)] or 10 μl ACSF (C) + microinjection of 100 μg l-glutamate sodium/1 μl ACSF into the PVH (, n = 8), third group, intraventricular injection of 10 μl AAVPS (A) or 10 μl AOXTS (B) or 50 μg naloxone/10 μl ACSF (C) + microinjection of 1 μl ACSF into the PVH (■, n = 8); and fourth group, intraventricular injection of 10 μl AAVPS (A) or 10 μl AOXTS (B) or 50 μg naloxone/10 μl ACSF (C) + microinjection of 100 μg l-glutamate sodium/1 μl ACSF into the PVH (○, n = 8). n indicates the animal number in each group. The results are showed as mean ± S.E.M. ^*P < 0.05, ^**P < 0.01 and ^***P < 0.001 are for the comparison of change of pain threshold (%) from the first group and other group; ⁺P < 0.05, ⁺⁺P < 0.01 and ⁺⁺⁺P < 0.001 are for the comparison of change of pain threshold (%) from the fourth group and the second group; P < 0.05, P < 0.01, and P < 0.001 are for the comparison of change of pain threshold (%) from the fourth group and the third group.